The invention relates to a floater-controlled flap valve for the filling pipe of a fuel tank. With valves of this type, the flow cross section of the filling pipe end that projects into the tank is formed by a pipe section, which can be closed off with a flap. The flap is positioned pivoting inside the pipe and extends through the pipe walls with two diametrically opposite arranged bearing journals. Two pivoting arms are formed onto the bearing journals on the outside of the pipe, which are hinged to the floater. The floater is positioned such that it can be displaced in axial direction along the periphery of the pipe section. The floater is lifted up when the fuel level rises. In the process, the pivoting arms are carried along and the flap is accordingly closed. While the flap is closed, the fuel that is pumped through a pump nozzle into the tank quickly rises inside the filling pipe, which then leads to the pump nozzle being shut off.
The fuel tanks used in present-day motor vehicles in most cases have very irregular shapes to allow for an optimum use of the space available inside the vehicle. Accordingly, the space available for installing components inside the fuel tank is frequently very small. A compact, space-saving installation method is therefore generally the goal when arranging components inside a fuel tank. The same holds true for the filling pipe section projecting into the tank or a flap valve.
It is the object of the invention to propose a flap valve of the aforementioned type with reduced structural length, meaning a more compact design.
This object is solved in that the floater, positioned at the end of the pipe section that projects at a slant into the inside space of the tank, is designed such that its lower front, as seen in the assembled state, essentially covers a horizontally extending frontal plane. Floaters for the flap valves in question have a hollow design and are open on the bottom. A floater of this type consequently does not start to swim upward until the liquid level encloses the air volume on the inside. The design according to the invention ensures that the aforementioned air volume is enclosed almost immediately and a liquid displacement can occur during a further rise in the fuel level, as soon as the fuel level reaches the area of the lower front edge region of the floater. If the front edge region of the floater does not have a level design and is not aligned horizontally, the wall areas of the floater are initially submerged into the liquid, without this resulting in a lifting force worth mentioning. On the contrary, the floaters in most cases are made of fuel-resistant polyoxymethylene (POM), a plastic with a higher specific weight than the fuel. These floater wall regions that are not effective for the lifting force not only extend the floater unnecessarily, but also represent a totally ineffective ballast that must be compensated by a corresponding floater volume, meaning the floater length. As a result of the slanted design or slanted arrangement of the floater according to the invention, said floater has a larger frontal surface that cooperates with the fuel level. The larger this surface, the shorter the submerging depth necessary for a predetermined lifting force. A shorter submerging depth with the same lifting force means a clearly improved response sensitivity of the flap valve.
The pivoting arms of the valve flap for the advantageous embodiment according to claim 2 are shorter than half the outside diameter of the pipe section. As a result, a reduced pivoting path is initially achieved for the free ends of the pivoting arms that are movement-connected to the floater. The displacement distance of the floater is accordingly shortened, which in turn favors a more compact design and improves the response sensitivity. More free space is created owing to the fact that the free ends of the pivoting arms do not project over the apex of the peripheral region of the pipe section arranged between the pivoting arms. This free space can be used to enlarge the floater and to arrange the floater as close as possible on the pipe section. An increased cross-sectional surface of the floater in turn means a lower submerging depth and thus a more compact design in longitudinal direction.
The modifications according to claims 3 to 5 make it easier to attach the floater to the pipe section.